Plasticized polyvinyl chloride compound

ABSTRACT

A highly flame retardant plasticized polyvinyl chloride compound (PVC) comprises a mixture of dialkyl tetrachlorophthalate and dialkyl tetrabromophthalate and is characterized by an absence of brittleness, and substantial flexibility at low temperatures as required for PVC formed jackets and insulation for wire and cable products.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a highly flame retardant plasticized polyvinylchloride compound (PVC) further characterized by an absence ofbrittleness at low temperatures, and substantial flexibility such asrequired for PVC formed jackets and insulation for wire and cableproducts and sheets often used, for example, as roof sheathing uponwhich shingles or other roof covering is laid.

2. Description of the Related Art

PVC compounds (PVC) are a well known class of thermoplastic polymerswhich exhibit excellent chemical and corrosion resistance, physical andmechanical strength, and electrical insulative properties. Unplasticizedversions of PVC are inherently flame resistant and rigid PVC compoundsrequire only additional antimony trioxide to achieve a high level offlame retardancy. However, when flexible forms of PVC are required, theaddition of plasticizers result in increased flammability of PVC.Conventional PVC is also apt to produce excessive smoke when ignited.

Both triaryl and diaryl alkyl phosphate esters have been used to improvethe flame retardancy of PVC. High flame retardant demands for morestringent flexible PVC applications, such as outer jackets andinsulators for plenum wires and cables, for sheets used in theconstruction industry, for example, as roof sheathing upon whichshingles or other roof coverings are laid, as well as for flexiblecoatings applied to fabrics, have required improvements in the flameretardant plasticizers incorporated in these compounds. The additionalof dialkyl tetrahalophthalates such as dioctyl tetrabromophthalate ordi-2-ethylhexyltetrabromophthalate have been able to achieve exceptionalthermal stability with exceptional flame retardancy. However, the lowtemperature flexibility of PVC compounds is compromised with theaddition of such compounds.

It is known that flame retardant synergy is exhibited by certainbrominated and chlorinated compounds. (By use of the term "flameretardant synergy" it is meant that the action of two or more substancesachieve an effect of which each is individually incapable.) For example,a paper entitled Bromine-Chlorine Synergy To Flame Retard ABS Resins, bySeunghee Yun and Hyunkoo Kim of Miwon Petrochemical Corporation,presented at the New Developments and Future Trends in Fire Safety On AGlobal Basis International Conference, March 1997, discusses mixtures ofDECHLORANE™ PLUS, a product of Occidental Chemical Corporation, and TBBA(Tetrabromobisphenol A), or FF-680 (Bis(Tribromophenoxy)Ethane) toproduce acrylonitrile butadiene styrene (ABS) resins having improvedflame retardant characteristics. However, the Yun and Kim results referto ABS, a rigid plastic used in electrical component housings (e.g. TVcabinets and computer casings). Yun and Kim use the chlorinatedsubstance Dechlorane Plus to increase the rigidity of the resultant ABS.Such rigidity would be a serious flaw in PVC formed jackets andinsulation for wire and cable products. Improvement of flame retardantproperties, as well as improvement of low temperature flexibility anddecreased smoke generation, has not heretofore been known when the typeof brominated and chlorinated compounds of the present invention areused in PVC compounds. The principal object of the present invention,therefore, is to provide a highly flame retardant plasticized PVC basedon the discovery that improved low temperature flexibility can beachieved by adding to PVC dialkyl tetrahalophthalate mixtures of thetype hereafter described.

Dialkyl tetrahalophthalates are produced from the reaction oftetrachlorophthalic acid or anhydride and/or tetrabromophthalic acid oranhydride with C₁ -C₁₈ alkanols. The production of dialkyltetrabromophthalate and dialkyl tetrachlorophthalates is well known inthe field. Numerous processes have been described for the preparation ofdialkyl phthalates by esterification of various alcohols with phthalicanhydride or acid in the presence of acidic catalysts, such as sulfuricacid, phosphoric acid, toluene sulfonic acid, and methane sulfonic acid.For example, Spatz et al. (I & EC Product Res. and Dev. 8: 391, 1969)discloses the preparation of di-2-ethylhexyl tetrabromophthalate usingphosphoric acid catalysis. Nomura et al. (published Japanese PatentApplication No. 50-05701, 1975) describes the use of tetraalkyltitanates in the presence of alkali metal salt to prepare dialkyltetrabromophthalates. Sagara et al. (U.S. Pat. No. 4,284,793) disclosesa method for producing plasticizers with low residual titanium, in whichphthalic anhydride is reacted with an alcohol in the presence of atitanate catalyst. The resultant ester is treated with a solid alkali,such as sodium carbonate, and adsorbing agent(s) in the absence ofwater. Watanable et al. (U.S. Pat. No. 4,304,925) discloses a processfor purifying esters, such as those formed from phthalic anhydride andethyl hexyl alcohol, when organotitanium compounds are used ascatalysts, where water is added to the esterification mixture and themixture is heated. Mamuzic et al. (U.S. Pat. No. 4,754,053) disclosesthe preparation of tetrabromophthalate diesters using sodium carbonatedecahydrate as an essential part of the process. Bohen et al. (U.S. Pat.Nos. 5,049,697 and 5,208,366) disclosed a process for the preparation ofdialkyl esters of polyhaloaromatic acids catalyzed by the use of variousorganometallic catalysts, such as organotitanates, as well asorgano-tin, antimony and zirconium compounds. However, these patents donot disclose nor suggest mixing tetrabromophthalate andtetrachlorophthalate for the purpose of improving low temperatureflexibility of PVC.

Accordingly, the primary object of this invention is to improve the lowtemperature flexibility of highly flame retardant plasticized PVCcompounds by incorporating into PVC, according to the discovery of theinvention, dialkyl tetrahalophthalate mixtures containing bothtetrabromophthalates and tetrachlorophthalates.

A further object of this invention is to decrease the smoke generationcharacter of PVC.

Another object is to provide an improved PVC approved for use inproducts such as insulation, jackets, coatings, and sheeting.

Other objects and advantages will be more fully apparent from thefollowing disclosure and claims.

SUMMARY OF THE INVENTION

The subject of this invention is to improve the low temperatureflexibility of highly flame retardant plasticized PVC compounds byincorporating into PVC dialkyl tetrahalophthalate mixtures containingboth tetrabromophthalates and tetrachlorophthalates. PVC containingtetrabromophthalate and tetrachlorophthalate mixtures show significantimprovements in their low temperature flexibility. PVC compounds of thepresent invention also result in synergist improvements of flameretardancy with decreased smoke generation.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS THEREOF

The principal object of this invention as previously stated is toimprove the low temperature flexibility of highly flame retardantplasticized PVC by the addition of dialkyl tetrahalophthalate mixtures.Preferably the dialkyl tetrahalophthalates used in the PVC compound ofthe present invention are prepared in accordance with the teachings ofthe separately filed co-pending patent application Ser. No. 08/554,262,which disclosed a new method for preparing nearly colorless, highlypure, tetrahalophthalates with an extremely low acid number. However, itis recognized that the dialkyl tetrahalophthalates used in the PVCcompound of the present invention may be prepared using methods alreadyknown in the art. When tetrahalophthalate compounds are made accordingto the method described in the '262 application, certain improvedcharacteristics of PVC useful to the present invention are achieved. Themethod for preparing dialkyl tetrahalophthalates as taught by the '262application is utilized by the present invention to produce thebrominated and chlorinated compounds which are incorporated into the PVCof the present invention resulting in an improved low temperatureflexibility characteristic. This method of the '262 application isdescribed next.

I. Preparation of Dialkyl Tetrahalophthalates

The preferred method as taught in the '262 application for preparingdialkyl tetrahalophthalates used in the present invention utilizes atetrahalophthalic compound selected from the group consisting oftetrahalophthalic anhydrides and tetrahalophthalic acids. Thetetrahalophthalic anhydride or acid used may be of tetrabromo- ortetrachloro-substitution on the aromatic ring, with tetrabromophthalicanhydride the preferred embodiment. The tetrahalophthalic compound isreacted with an excess of alkanol, as is known in the art, to form areaction mass. The alkanol is selected from C₁ to C₁₈ alkanols, or amixture thereof. The alkanol may be a C₁ to C₁₈ primary or secondaryalkanol with linear or branched alkyl moieties. The preferred alkanolsare 2-ethylhexanol and 3,3,5-trimethylhexanol, as well as mixtures of C₁to C₁₈ alkanols resultant from Oxo- and Ziegler manufacturing processesas known in the art (see Weissermel, K. and Arpe, H-J., IndustrialOrganic Chemistry, pages 132-134, 206-208, VCH Publishers, New York,1978).

The tetrahalophthalic anhydride may contain up to 0.30% residualsulfuric acid. Residual sulfuric acid resultant from the preparation ofthe original tetrahalophthalic anhydride is removed by serial hot waterwashing or preferably by the neutralization with a first Group II alkalimetal salt, more preferably a Group II alkali metal salt of a lowercarbon chain acid, and most preferably magnesium or calcium acetate.This treatment must be done before esterification to achieve low productcolor. Lower carbon chain acids of the type identified herein are carbonchains containing approximately four or less carbons. If hot water isused (about 90° C.), typically 3-4, 300-ml aliquots of water (usuallyabout 1 part water to 2 parts anhydride+alkanol) have been found to besufficient to remove the residual sulfuric acid in the aqueous phase toless than 0.1%, when a mole of anhydride is used in the startingreaction mix. If less water is used, more washes are generally requiredto achieve the results of the invention. The water wash treatment, whilebeing effective, is substantially more time-consuming than adding aGroup II alkali metal salt, which is the preferred treatment

Preferably, treatment first with a Group II alkali metal salt (firstGroup II alkali metal salt) is used instead of a water wash to removeacidity. A weak base is preferred, such as magnesium acetate, toneutralize the acid. Alternatively, calcium acetate may be used. Use ofan acetate ensures that the pH will be less than 7.0 which is criticalbecause the titanium catalyst is sensitive to, and is destroyed by,alkaline pH. The first Group II alkali metal salt is used at 0.01 to 10percent of the weight of the reaction mass (defined as the weight of theoriginal reactants, preferably at 0.1 to 0.5 weight percent, mostpreferably at stoichiometric levels equal to that of the residualsulfuric acid in the tetrahalophthalic anhydride.

The solution which has been water washed or treated with a first GroupII alkali metal salt is dried by azeotroping out the water to a contentof less than 0.05% by means known in the art. The product is thenesterified with a neutral catalyst which may be an alkyl titanatecatalyst or zirconium tetrabutoxide. An alkyl titanate catalyst isnormally used in the industry. The esterification catalyst is a C₁ toC₁₈ tetraalkyl titanate, preferably a C₈ to C₁₈ tetraalkyl titanate,which most preferably is an alkyl identical to that of the alkanolesterified into the product, thereby limiting the preparation of mixedesters due to the transesterification of the alkyl groups of thecatalyst into the product.

The esterification is carried out in an inert atmosphere, such as argonor nitrogen, at 160-240° C., preferably at 190-210° C. An azeotropicsolvent or entrainer, such as a non-reactive aromatic or aliphatichydrocarbon, for example, xylene or toluene as is known in the art, isadded to shorten the esterification time. An inert carrier gas, such asargon, nitrogen, or carbon dioxide, may be used to drive off thereaction water formed during the esterification. The esterification iscontinued until residual acidity drops to less than 1.0 meq/100 gramsample, preferably less than 0.5 meq/100 gram sample at which time theexcess alkanol is removed by vacuum distillation. This vacuumdistillation decreases the residual acidity to less than 0.2 meq/100gram sample. Excess alcohol must be removed to increase flash point anddecrease volatility of the finished product.

In another important step, the residual acidity from the reaction isremoved by the addition of 0.1 to 20 percent of a second Group II alkalimetal salt, such as magnesium silicate (Magnesol® from the Dallas Group)or calcium silicate, plus an equal weight of water. This step is doneafter esterification; otherwise, the tetrahalo anhydride would beunnecessarily treated, which would consume raw material needlessly.Magnesium silicate makes the salts of titanium insoluble so that more ofthe turbidity-causing titanium drops out of the solution. Althoughmagnesium or calcium oxide, or magnesium or calcium hydroxide, may beused at an equal weight percent basis as the magnesium silicate, thereis a resultant decrease in filtration rates. Use of Group I alkalis,other than lithium hydroxide and lithium silicate is not desirablebecause of their alkalinity (loss of product yield with poorfiltration), and some metal contamination (Lithium and titanium) occurswith the lithium alkalis.

The addition of the water in the step discussed above is essential forthe neutralization of the residual acidity by the magnesium silicate.Further, the water neutralizes the residual unreacted monoesterintermediate. Water acts as a phase transfer agent. Magnesium silicateis a powder. The reaction conditions are 50-95° C., preferably 90° C.for 1 to 4 hours after which the water of the neutralization is removedby vacuum distillation at 90-140° C. This drying technique is essentialto driving the neutralization to completion as well as the formation ofa granular precipitant which is easily removed with conventionalfiltration methods, such as vacuum or pressure filtration. The finalproduct of the invention can be washed again with lithium hydroxide ifit is desired to increase the product purity and assure the minimumlevel of acidity.

The treatment with magnesium silicate decreases product color 1 to 5Gardner color units (A.O.C.S. Method Td 12-64T) as compared to 5-15Gardner color units. This treatment essentially removes all residualtitanium, thus producing a haze-free product even at low temperatures.These Group II alkali metal silicates are particularly advantageoussince filter aids, such as diatomaceous earth, are not required and theGroup II alkali metal silicate absorbs only small quantities of finishedproduct, thereby improving product yield.

Products prepared according to the described method have a purity of93-95.5%, with an average of 95-95.5%, whereas prior methodologies attheir best have only reached a purity of about 93%.

The Gardner color units of the final product are decreased to about 10without the water wash or magnesium acetate but with the magnesiumsilicate (as compared to about 15 without either treatment). The waterwash or the magnesium acetate treatment plus the magnesium silicatetreatment decreases the Gardner color units to about 1-2.

The features and advantages of the described method of the '262application as applied to the present invention will be more clearlyunderstood by reference to the following examples, which are not to beconstrued as limiting to the present invention.

EXAMPLES Example I

1. Tetrabromophthalic anhydride (464 grams), which typically contains0.08-0.15% sulfuric acid, is dissolved in 2-ethylhexanol (390 grams) at90° C. as is known in the art.

2. The solution is serially washed with aliquots of 300 grams of hotwater at 90° C. until the residual sulfuric acid in the aqueous phase isless than 0.1%.

3. The solution is dried by azeotroping out water at 160-190° C. untilthe water content is less than 0.05%.

4. The reaction mass is esterified at 195-205° C. in a 1 liter reactionflask equipped with a Dean-Stark trap, with a catalytic quantity oftetra-2-ethylhexyl titanate (6 grams) until residual acid values areless than 0.5 meq/100 grams sample. The total esterification time isless than 6 hours.

5. The excess 2-ethylhexanol is distilled off under vacuum, furtherreducing the residual acidity to less than 0.2 meq/100 grams sample.

6. The reaction mass is cooled to 90° C. and treated with 7 gramsmagnesium silicate and 7 grams water, each of which is slurried into thereaction mass with mixing. The amount of water preferred is 1-2 timesthat of magnesium silicate (at 0.1 to 20 weight percent). The acid valueis checked before filtration (next step) to be sure that it is low.

7. After treatment the reaction mass is dried under vacuum to less than0.05% water and vacuum-filtered hot with a Buchner funnel as known inthe art. The resulting product (692 grams) has the following properties:

Appearance: Clear, slightly yellow liquid with no haze

Gardner Color: <1

Acidity: <0.001 meq/100 gram sample (ASTM D 1613-91)

GC Purity: 97.4%

Residual Titanium: <0.1 ppm (lower detection limit)

Residual Magnesium: <0.1 ppm (lower detection limit)

Example II

The serial water washing of Example I (step 2) is replaced with theaddition of 1.5 grams magnesium acetate. The resultant product is nearlycolorless with equal product quality properties and yield as in Example1.

Example III

The 2-ethylhexanol of Examples I or II is replaced with a mixture ofstraight and branched chain alcohols (480 grams) with nine to elevencarbons (e.g., Neodol 91 manufactured by Shell Chemical Company). Theresultant product quality is comparable to the results of Examples I andII with a product yield of 750 grams. Product purity was slightly lowerdue to the mixed esters produced from the transesterification of thealkyl groups of the catalyst.

Example IV

The 2-ethylhexanol of Examples I or II is replaced with 432 grams of3,3,5-trimethyhexanol (also known as isononyl alcohol). The resultantproduct quality is comparable to the above examples with a product yieldof 719 grams. Product purity is slightly lower due to the mixed estersproduced from the transesterification of the alkyl groups of thecatalyst.

Example V

The 2-ethylhexanol of Examples I or II is replaced with a mixture ofstraight and branched chain alcohols (516 grams) with eleven carbons(comparable to Neodol 1 manufactured by Shell Chemical or Lial 111manufactured by EniChem). The resultant product quality is comparable tothe above examples with a product yield of 774 grams. Product purity isslightly lower due to the mixed esters produced from thetransesterification of the alkyl groups of the catalyst.

Example VI

The 2-ethylhexanol of Examples I or II is replaced with a isodecylalcohol (comparable to Exxal 10 manufactured by Exxon Chemical)(474grams). The resultant product quality is comparable to the aboveexamples with a product yield of 764 grams. Product purity is slightlylower due to the mixed esters produced from the transesterification ofthe alkyl groups of the catalyst.

Example VII

The 2-ethylhexanol of Examples I or II is replaced with isotridecylalcohol (comparable to Exxal 13 manufactured by Exxon Chemical)(600grams). The resultant product quality is comparable to the aboveexamples with a product yield of 828 grams. Product purity is slightlylower due to the mixed esters produced from the transesterification ofthe alkyl groups of the catalyst.

Example VIII

The 2-ethylhexanol of Examples I or II is replaced with n-octanol(comparable to Alfol 8 manufactured by Vista Chemical or Epal 8manufactured by Amoco)(390 grams). The resultant product quality iscomparable to the above examples with a product yield of 695 grams.Product purity is slightly lower due to the mixed esters produced fromthe transesterification of the alkyl groups of the catalyst.

From the above it can be seen how nearly colorless, highly pure, dialkyltetrahalophthalates with an extremely low acid number were preparedaccording to the '262 application. The description next proceeds todescribing how plasticized PVC compounds of the present invention areprepared.

II. Preparation of Plasticized PVC Compounds

In the present invention, dialkyl tetrachlorophthalate and dialkyltetrabromophthalate are first individually prepared in accordance withthe above described method. Following which, in accordance with thepresent invention, the dialkyl tetrachlorophthalate-dialkyltetrabromophthalate mixture can be prepared in any of a number of ways.For example, the two tetrahalophthalate products may be preparedseparately and then mixed until a homogeneous one phase fluid isobtained. The two products may also be synthesized simultaneously. Themixtures can be prepared by synthesizing separately or together, bymixing the appropriate molar ratio of tetrachlorophthalic andtetrabromophthalic anhydrides with the C₁₋₁₈ alkanol in a reaction flaskas described in detail above. As is well known in the arts, flameretardants must be in liquid form to plasticize PVC. See, Handbook ofPolyvinyl Chloride Formulating, edited by Edward J. Wickson, 818-831,John Wiley & Sons (1993). The disclosure of this publication and allother publications and patents referred to herein are incorporatedherein by reference.

The tetrahalophthalate mixture is then added and mixed with PVC, a flameretardancy synergist such as antimony trioxide, a plasticizer such astrioctyl trimellitate, and a lead stabilizer which are compounded into aflexible thermoplastic polymer, such as PVC for use on plenum wire andcable applications, where low-temperature flexibility is a desired PVCattribute. The dialkyl tetrahalophthalate mixtures can comprise dialkyltetrachlorophthalate to dialkyl tetrabromophthalate of 1-99% to 99-1% byweight. However, the ratio of these two halophthalates is preferably1-50% dialkyl tetrachlorophthalate to dialkyl tetrabromophthalate, but25-33% dialkyl tetrachlorophthalate to dialkyl tetrabromophthalate ismost preferred.

EXAMPLES

For Examples A, B, and C below, composition components (base PVCpolymer, plasticizer, stabilizer, flame retardant synergist, and thedialkyl tetrahalophthalate mixture) were combined and thoroughly mixed.Initial mixing of the ingredients was done in a blender. The resultingcharge was transferred to a 2 roll mill and preheated to 350° F. forfusion and further mixing. Rolling time was for 5 minutes under 1260 psicompression at 337° F. for compression molding of the mixture into testsheets. The standard for PVC compression molding as known in the art isfully described in ASTM Designation: D-1928-90 and ASTM D-746. ASTMD-1928-90 and ASTM D-746 disclose the standard for preparing compressionmolded polyethylene test sheets and is also the standard for PVCcompression molding of the mixture into test specimens which, in thiscase, were subjected to physical, mechanical, and flame retardancytesting as described in Examples A, B, and C below.

Each Example includes tests to determine the tensile properties of thecompressed PVC using standard dumbbell-shaped test specimens. Thestandard test method for testing tensile properties is found in the ASTMDesignation D-638, published in 1995. In summary, the test specimen isclamped by and between grips. The grips extend in opposed directionsthereby stretching the test specimens until the specimen breaks. Thetest specimens' tensile properties that were measured were: (1) TensileModulus, which is the ratio of stress to corresponding strain below theproportional limit of a material, expressed in force per unit area; (2)Tensile Strength at Break, which is the maximum tensile stress (tensileload per unit area of minimum original cross section) sustained by thespecimen during a tension test at specimen break; and (3) Elongation,which is the elongation of a test specimen expressed as a percent of thegage length. An increase in these test factors indicates a more flexibletest specimen

Test specimen hardness was also measured. The standard hardness testmethod is found in the ASTM D-2240, published in 1995. In summary, thetest method results are based on the penetration of a indentor whenforced into the test specimen.

Flame retardancy of the control and test formulations were determined bythe Designation ASTM D-2863, published in 1995, to give oxygen indexvalues. The oxygen index is equal to the minimum concentration ofoxygen, expressed as volume percent, in a mixture of oxygen and nitrogenthat will just support flaming combustion of a material initially atroom temperature. A higher oxygen index indicates higher flameretardancy.

The test specimens were tested for the density of smoke generated byburning the test specimens in an NBS Smoke Chamber using the flamingmode in accordance with the ASTM E662-95 publication.

The test specimens were also tested for Brittleness Temperature.Brittleness temperature is the temperature at which 50% of the specimensprobably would fail. The brittleness of a test specimen is determined byimmersing the specimen in a bath containing a heat transfer medium thatis cooled. The specimens are struck at striking element at specifiedlinear speed and then examined. The brittleness temperature is thetemperature at which 50% of the specimens fail.

EXAMPLE A

PVC resin (the base PVC resin used was GEON 30, a product of the GEONCOMPANY) was compounded in a 2 roll mill in accordance with theprocedures disclosed in ASTM D-1928 using the below mentioned Controland Test Formulations. The quantities of components are indicated inparts by weight per hundred parts by weight resin.

    ______________________________________                                        Formulations                                                                  ______________________________________                                                      CONTROL                                                            FORMULATION                                                                   Parts per TEST FORMULATION                                                    Hundred Parts per Hundred Resin                                              COMPONENT Resin (PHR) (PHR)                                                 ______________________________________                                          PVC Resin (Geon 30) 100 100                                                   Antimony Trioxide 15 15                                                       Trioctyl Trimellitate 34.3 34.3                                               (UNIPLEX ™ 546-A)                                                          Lead Stabilizer 5 5                                                           Dioctyl                                                                       Tetrabromophthalate 40 30                                                     (UNIPLEX ™ FRP-45)                                                         Dioctyl                                                                       Tetrachlorophthalate 0 10                                                     (UNIPLEX ™ FRP-27)                                                       ______________________________________                                           CONTROL TEST                                                                 TEST PROCEDURE FORMULATION FORMULATION                                      ______________________________________                                          Tensile Modulus at 100% 1760 1963                                             Strain (psi) (ASTM                                                            D638-95)                                                                      Tensile Strength at Break 2050 3391                                           (ASTM D638-95)                                                                Elongation (%) 278 370                                                        (ASTM D638-95)                                                                Shore A Hardness 88 94                                                        (ASTM D-224095, A                                                             Scale)                                                                        Oxygen Index 33 37                                                            (ASTM D2863-95)                                                               NBS Smoke 440 276                                                             (ASTM E662-95) Flaming                                                        (Dmc)                                                                         Non-flaming (Dmc) 180 140                                                     Brittleness -14 -25                                                           Temperature                                                                   Testing, °C.,                                                          (ASTM D746-95)                                                              ______________________________________                                    

EXAMPLE B

Dialkyl tetrabromophthalates were prepared from the reaction of LINEVOL™911 alcohol (produced by SHELL CHEMICAL, CAS Registry Number is68603-15-6) with tetrabromophthalic anhydride to produce adi(nonyl/decyl/undecyl) tetrabromophthalate mixture in accordance withthe preferred method of producing dialkyl tetrahalophthalates describedabove. LINEVOL™ 911 is a mixture of nonyl(C₉), decyl (C₁₀), and undecyl(C₁₁) alcohols with 75-85% by weight normal alcohols and the remainderbeing 2-n-alkylisomers, principally 2-methyl. Since tetrahalophthalateanhydride has two reactive acid functions; dialkyl tetrahalophthalatesare produced as illustrated immediately below: ##STR1## Where R=C₉ orC₁₀ or C₁₁. Where R'=C₉ or C₁₀ or C₁₁.

Where X=halogen.

Therefore, there are seven different diesters possible where the alkanolcarbon chain lengths are:

di C₉, C₉ C₁₀, C₉ C₁₁

di C₁₀, C₁₀ C₁₁

di C₁₁, C₁₁,C₉

In this case, the resultant brominated diesters were mixed with thedioctyl tetrachlorophthalate, preferably prepared in accordance with themethod for producing dialkyl tetrahalophthalates described above, atroom temperature until a homogeneous one phase liquid mixture wasproduced. The tetrahalophthalate mixture was then compounded into PVC aspreviously described and as is well known in the art.

    ______________________________________                                        Formulations:                                                                 ______________________________________                                                     CONTROL                                                             FORMULATION TEST FORMULATION                                                  Parts per Hundred Parts per Hundred Resin                                    COMPONENT Resin (PHR) (PHR)                                                 ______________________________________                                          PVC Resin (Geon 30) 100 100                                                   Antimony Trioxide 15 15                                                       Trioctyl Trimellitate 34.3 34.3                                               (UNIPLEX ™ 546-A)                                                          Lead Stabilizer 5 5                                                           Di(nonyl/decyl/undecyl) 40 30                                                 Tetrabromophthalate                                                           Dioctyl 0 10                                                                  Tetrachlorophthalate                                                          (UNIPLEX ™ FRP-27)                                                         UNIPLEX is a                                                                  trade name                                                                    for the named                                                                 compound owned                                                                by Unitex                                                                     Chemical                                                                      Corporation.                                                                ______________________________________                                           CONTROL TEST                                                                 TEST PROCEDURE FORMULATION FORMULATION                                      ______________________________________                                          Tensile Modulus 1800 1960                                                     at 100%                                                                       Strain (psi) (ASTM                                                            D638-95)                                                                      Tensile Strength 2010 3410                                                    at Break                                                                      (ASTM D638-95)                                                                Elongation (%) 284 385                                                        (ASTM D638-95)                                                                Shore A Hardness 88 94                                                        (ASTM D-224095, A                                                             Scale)                                                                        Oxygen Index 33 37                                                            (ASTM D2863-95)                                                               NBS Smoke 460 284                                                             (ASTM E662-95)                                                                Flaming                                                                       (Dmc)                                                                         Non-flaming (Dmc) 200 140                                                     Brittleness -21 -34                                                           Temperature                                                                   Testing, °C.,                                                          (ASTM D746-95)                                                              ______________________________________                                    

EXAMPLE C

PVC resin (Geon 30 from the Geon Company was compounded in a 2 roll millby ASTM D 746 using the below mentioned formulations.

    ______________________________________                                                                   PARTS PER                                             PARTS PER HUNDRED HUNDRED RESIN                                              COMPONENT RESIN (PHR) (PHR)                                                 ______________________________________                                        PVC Resin (Geon 30)                                                                       100            100                                                  Antimony Trioxide 15 15                                                       Trioctyl Trimellitate 34.3 34.3                                               (Uniplex 546-A)                                                               Lead Stabilizer 5 5                                                           Dioctyl 20 10                                                                 Tetrabromophthalate                                                           (Uniplex FRP-45)                                                              Dioctyl 20 30                                                                 Tetrachlorophthalate                                                          (Uniplex FRP-27)                                                            ______________________________________                                    

The resultant resin was compression molded into test specimens andsubject to physical, mechanical, and flame retardancy testing. Theresults are shown in the table below:

    ______________________________________                                                       PARTS PER    PARTS PER                                            HUNDRED RESIN HUNDRED RESIN                                                  TEST PROCEDURE (PHR) (PHR)                                                  ______________________________________                                        Tensile Modulus at 100%                                                                      2050         2180                                                Strain (psi) (ASTM D638-                                                      95)                                                                           Tensile Strength at Break 3450  3560                                          (ASTM D638-95)                                                                Elongation (%) (ASTM 385 390                                                  D638-95)                                                                      Shore A Hardness (ASTM  94  94                                                D-224095, A Scale)                                                            Oxygen Index (ASTM  41  44                                                    D2863-95)                                                                     NBS Smoke (ASTM 270 220                                                       E662-95) Flaming (Dmc)                                                        Non-flaming (Dmc) 130 110                                                     Brittleness Temperature -28 -32                                               Testing, °C., (ASTM -28 -32                                            D746-95)                                                                    ______________________________________                                    

As illustrated by the Examples A, B, and C for the preparation of theplasticized PVC of the present invention, PVC mixtures oftetrabromophthalates and tetrachlorophthalates can be used to formhighly flame retardant plasticized PVC with improved low temperatureflexibility. As a related discovery, it has also been found that PVC ofthe present invention also result in less than normal smoke generationwhen ignited.

While the invention has been described with reference to specificembodiments thereof, it will be appreciated that numerous variations,modifications, and embodiments are possible, and accordingly, all suchvariations, modifications, and embodiments are to be regarded as beingwithin the spirit and scope of the invention.

What is claimed is:
 1. A flame retarded plasticized flexible compositioncomprising:a. a polyvinyl chloride resin; b. a flame retardantsynergist; c. a stabilizer; and d. a mixture comprising:i.tetrachlorophthalate; and ii. tetrabromophthalate; saidtetrachlorophthalate and said tetrabromophthalate being proportioned inamounts effective to impart to said composition when subjected to asubstantially low temperature a degree of flexibility, as exhibited byits brittleness, which is substantially greater than the degree offlexibility exhibited by said composition at said low temperature wheneither said tetrachlorophthalate or said tetrabromophthalate is notincluded in said mixture.
 2. A flame retarded plasticized flexiblecomposition as recited in claim 1, wherein in said mixture saidtetrachlorophthalate is incorporated with said tetrabromophthalate inthe ratio of 1-99% to 99-1% by weight.
 3. A flame retarded plasticizedflexible composition as recited in claim 1, wherein in said mixture saidtetrachlorophthalate is incorporated with said tetrabromophthalate inthe ratio of 1-50% by weight.
 4. A flame retarded plasticized flexiblecomposition as recited in claim 1, wherein in said mixture saidtetrachlorophthalate is incorporated with said tetrabromophthalate inthe ratio of 25-33% by weight.
 5. A flame retarded plasticized flexiblecomposition as recited in claim 1, wherein said tetrachlorophthalate andsaid tetrabromophthalate are each prepared in accordance with theprocess, comprising:a. dissolving a tetrahalophthalic compound selectedfrom the group consisting of tetrahalophthalic anhydrides andtetrahalophthalic acids, in a C₁ -C₁₈ alkanol, to form a reaction mass,which includes residual sulfuric acid; b. removing said residualsulfuric acid from the reaction mass using a treatment selected from thegroup consisting of serial water washes, and treatment with a firstGroup II alkali metal salt of a low number carbon chain organic acid; c.removing water from said reaction mass; d. esterifying with an alkyltitanate catalyst; and e. treating with a second Group II alkali metalsalt and water to decolorize and remove residual metal contamination andacidity.
 6. A flame retarded plasticized flexible composition as recitedin claim 1, wherein the amounts in which said tetrachlorophthalate andsaid tetrabromophthalate are proportioned are also effective to impart asubstantial reduction in smoke formation of said composition whenignited, which reduction is substantially greater than the reduction insmoke formation of said ignited composition when either saidtetrachlorophthalate or said tetrabromophthalate is not included in saidmixture.
 7. A flame retarded plasticized flexible composition as recitedin claim 1, wherein the amounts in which said tetrachlorophthalate andsaid tetrabromophthalate are proportioned are also effective to impart asubstantial increase in fire retardancy of said composition, whichincrease is substantially greater than the increase in fire retardancyof said composition when either said tetrachlorophthalate or saidtetrabromophthalate is not included in said mixture.
 8. A process ofpreparing a flame retarded plasticized flexible composition comprisingthe following steps:a) providing a polyvinyl chloride resin; and b)mixing a flame retardant synergist stabilizer, tetrachlorophthalate, andtetrabromophthalate with said polyvinyl chloride resin, wherein saidtetrachlorophthalate and said tetrabromophthalate are each preparedby:(i) dissolving a tetrahalophthalic compound selected from the groupconsisting of tetrahalophthalic anhydrides and tetrahalophthalic acids,in a C₁ -C₁₈ alkanol, to form a reaction mass; (ii) removing residualsulfuric acid from the reaction mass using a treatment selected from thegroup consisting of serial water washes, and treatment with a firstGroup II alkali metal salt of a low number carbon chain organic acid;(iii) removing water from said reaction mass; (iv) esterifying with analkyl titanate catalyst; and (v) treating with a second Group II alkalimetal salt and water to decolorize and remove residual metalcontamination and acidity.